The human nail is very porous and becomes more so with age. This porosity increases the tendency of nails to stain. Staining may be caused by the repeated use of nail lacquer over a prolonged period of time, nicotine from handling lighted cigarettes, or from various chemicals to which people may be exposed in their homes or occupations. Nails also yellow with age due to melamine, a brown pigment synthesized in the body by normal biological processes and carried up into the nails from the nail beds. The stains due to nail lacquers are believed to be caused by bleeding of pigmentary materials such as partially solubilized dyes into the nail. In addition, the nitrocellulose found in the nail lacquers is known to heavily contribute to nail staining. The esthetically displeasing result of stained nails has lead to different nail stain removers.
Many of the standard preparations use bleaches which are extremely drying and irritating to nails. Preparations containing strong alkali such as sodium hydroxide or alkali metal hydroxides are also known. For obvious reasons these preparations are not desirable.
In U.S. Pat. No. 4,344,932 a nail cleanser comprised of chelating agents such as EDTA and urea in a liquid carrier is disclosed. The chelating agents remove stains by complexing with the metal ions which are present in many nail stains. However some stains, such as residual dyestuffs left on nails due to lacquers, do not respond as effectively to chelating agents alone, thus resulting in a less effective cleanser. Further, urea is often irritating to tissues surrounding the nail so it is desirable to find nail cleansing preparations which avoid these drawbacks.